Skip the auto shop - Our mechanics make house calls

Q: Engine over-heating and Radiator then overflows fluid or steam.

asked by on

We have by-passed the usual route for powering the cooling fan. We are using a switch placed on top of the front fender from the car battery to power the cooling fan "by hand". It seems the engine overheats very quickly, maybe at about 4 miles & definitely by a 10 mile trip on the road, & when it does the radiator starts spilling over with fluid or steaming. You can hear the fluid inside the radiator boiling. We replenish the radiator fluid after one of these leaks & keep driving until it overheats again. I had a simple test done that indicates the head gaskets are still good. The Engine & transmission seem strong, so we don't want to ruin the engine. Someone said he thought there was a leak at the top of the radiator, told me that if we keep over-heating the engine, it will weaken the engine. IS that true? WE need this vehicle for short hauling trips almost every day!. What should we do to fix this that hopefully isn't going to cost more than the van or a newer one?

My car has 182000 miles.
My car has an automatic transmission.

A: First of all, overheating the engine will d...

First of all, overheating the engine will damage it. The list of reasons why is long, but here is a partial list of reasons why overheating the engine will ruin it.

  • The engine oil becomes much thinner at higher temps.
  • The engine oil can bake on to metal parts
  • Engines have very tight spaces for pressurized oil to lubricate the parts. When the engine is too hot, these spaces become smaller, or disappear all together.
  • Gaskets fail easier.
  • Metal parts can become warped.
  • You can overheat the transmission by overheating the engine. First of all they are bolted together and share the heat. Second, the cooler lines from the transmission go to the radiator to be cooled. When the radiator is boiling, this cooks the transmission fluid. Too much heat is the number one problem with transmission failure.

Second, there really isn't such a thing as weakening it, it's either runs well, or it doesn't. Considering that the engine is over heating in such a short time and distance, I would assume that the coolant is not circulating. The first and easiest part to check or replace would be the thermostat (as needed). While the engine is running and full of coolant, feel the upper and lower radiator hoses. If one is hot, and the other is not, the thermostat might be stuck closed.

Finally, I believe, based on my gut feeling, that the the water pump has failed. I have seen the impeller that circulates the coolant come off before. When this happens, the coolant does not circulate. It will heat up quickly when it can not reach the radiator. It will then boil. This does not happen at 212 degrees. A 50/50 mix of coolant and water, under 16 psi of pressure, will boil around 260 degrees. This creates extra pressure in the system. The radiator cap is designed to release any pressure over it's rating into the coolant reservoir. It will quickly overflow under these circumstances. The cooling fan that you hard wired will not do much of anything because the hot coolant in the engine never gets to the radiator, until its too late and boiling. You can confirm this when the engine is hot, the fan will be blowing cold air.

I would not delay having this repaired. Consider having a certified mechanic, such as one from YourMechanic, come by and address your overheating concerns.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Check Engine code for catalytic converter.

This can be because the catalytic converter is bad or the sensor is defective. A qualified mechanic would have to scan the vehicle and check for broken up or rattling converter signifying its coming apart inside.

Q: Radiator replacement on the car

You should have no problem getting an aftermarket radiator for the vehicle. The radiator from the dealer or aftermarket is okay to use. The aftermarket one may save you money. I cannot state the quality for any of them since...

Q: Have hole intop plastic radiator how can i mend till i can get a new radiator

There is a compound called JB Weld that might work to fix a small hole in a radiator temporarily. This compound has two parts a black and a grey. When the two are mixed together, this creates the compound. Once...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...